﻿60 
  Dr. 
  G. 
  Baur 
  on 
  the 
  

  

  It 
  is 
  only 
  in 
  the 
  Testudinidse 
  among 
  the 
  Cryptodira 
  that 
  

   we 
  find 
  forms 
  with 
  pterygoids 
  not 
  emarginate 
  in 
  front. 
  Tes- 
  

   tudo 
  tabulata 
  and 
  some 
  of 
  the 
  gigantic 
  tortoises 
  show 
  it 
  

   especially. 
  

  

  T 
  cannot 
  give 
  much 
  value 
  to 
  the 
  apparent 
  expansion 
  at 
  the 
  

   posterior 
  half 
  of 
  the 
  pterygoids 
  ; 
  it 
  may 
  be 
  that 
  it 
  is 
  produced 
  

   by 
  crushing 
  of 
  the 
  edges, 
  and 
  even 
  if 
  it 
  were 
  natural, 
  it 
  

   would 
  not 
  be 
  of 
  great 
  importance 
  ; 
  the 
  Trionychoidea 
  show 
  

   all 
  stages 
  of 
  these 
  expansions 
  ; 
  in 
  some 
  we 
  have 
  no 
  trace, 
  in 
  

   others 
  they 
  are 
  very 
  well 
  developed. 
  

  

  The 
  hyoid 
  bones 
  of 
  Meiolania 
  are 
  of 
  the 
  same 
  form 
  as 
  in 
  

   the 
  Testudinidse. 
  

  

  The 
  anterior 
  nasal 
  opening 
  in 
  Meiolania 
  platyceps 
  is 
  divided 
  

   by 
  a 
  process 
  connecting 
  the 
  premaxillaries 
  with 
  the 
  pre- 
  

   frontals. 
  

  

  In 
  Meiolania 
  Oweni 
  this 
  process 
  is 
  interrupted 
  in 
  the 
  

   middle. 
  

  

  Indications 
  of 
  such 
  processes 
  showing 
  a 
  tendency 
  to 
  divide 
  

   the 
  anterior 
  nasal 
  openings 
  we 
  find 
  only 
  in 
  the 
  Testudinidse. 
  

   In 
  most 
  of 
  these 
  a 
  sharp 
  ascending 
  process 
  is 
  developed 
  from 
  

   the 
  premaxillaries, 
  and 
  also 
  one 
  descending 
  from 
  the 
  anterior 
  

   end 
  of 
  the 
  prefrontals. 
  

  

  There 
  may 
  be 
  an 
  objection 
  ; 
  the 
  fissure 
  for 
  the 
  stapes 
  in 
  

   the 
  quadrate 
  is 
  open 
  in 
  Meiolania, 
  closed 
  in 
  all 
  the 
  known 
  

   Testudinidse, 
  so 
  far 
  as 
  I 
  am 
  aware. 
  An 
  open 
  fissure 
  of 
  course 
  

   is 
  the 
  original 
  condition. 
  But 
  if 
  we 
  have 
  in 
  one 
  family 
  — 
  the 
  

   Chelydridse 
  — 
  both 
  conditions, 
  we 
  cannot 
  lay 
  very 
  much 
  stress 
  

   upon 
  that. 
  Chelydra 
  and 
  Macrochelys 
  have 
  the 
  fissure 
  

   closed, 
  Toxochelys 
  has 
  it 
  open. 
  

  

  Another 
  objection 
  may 
  be 
  that 
  there 
  is 
  not 
  a 
  single 
  form 
  of 
  

   the 
  Testudinidse 
  with 
  the 
  temporal 
  fossae 
  completely 
  arched 
  

   over 
  and 
  with 
  the 
  quadratojugal 
  region 
  so 
  much 
  developed 
  as 
  

   in 
  Meiolania. 
  

  

  Of 
  course 
  there 
  is 
  none 
  ! 
  But 
  in 
  Meiolania 
  we 
  have 
  to 
  

   distinguish 
  between 
  true 
  ossifications 
  of 
  the 
  skull 
  and 
  dermal 
  

   ossifications 
  ! 
  

  

  / 
  believe 
  that 
  the 
  whole 
  posterior 
  half 
  of 
  the 
  skidl 
  of 
  Meio- 
  

   lania 
  is 
  modified 
  by 
  the 
  enormous 
  development 
  and 
  extension 
  of 
  

   dermal 
  ossifications, 
  in 
  the 
  same 
  way 
  as 
  the 
  skull 
  of 
  Phryno- 
  

   soma. 
  

  

  In 
  some 
  of 
  the 
  Lacertilia 
  we 
  have 
  only 
  horny 
  scales, 
  with- 
  

   out 
  any 
  ossifications 
  ; 
  in 
  Phrynosoma, 
  however, 
  we 
  find 
  

   ossified 
  horn-cores 
  not 
  separable 
  from 
  the 
  bones 
  of 
  the 
  skull. 
  

  

  I 
  think 
  that 
  the 
  dermal 
  ossifications 
  in 
  the 
  skull 
  of 
  Meio- 
  

   lania 
  have 
  originated 
  in 
  the 
  same 
  way 
  as 
  I 
  have 
  indicated 
  

  

  